From c0c532551afc0279ebf2fd7bf460a075044ef50a Mon Sep 17 00:00:00 2001
From: Benoit Papillault <benoit.papillault@free.fr>
Date: Fri, 16 Apr 2010 00:07:26 +0200
Subject: [PATCH] --- yaml --- r: 194453 b: refs/heads/master c:
 1c0fc65e6de4e941ff483df445e721d6edb1f84b h: refs/heads/master i:   194451:
 3ca862066dd7a3594375672766098f63d4feb570 v: v3

---
 [refs]                                     |  2 +-
 trunk/drivers/net/wireless/ath/ath5k/pcu.c | 31 ++++++++++++++++++++--
 trunk/drivers/net/wireless/ath/ath9k/hw.c  | 19 ++++++++++---
 3 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/[refs] b/[refs]
index ce0c44afc865..4c581d5623ff 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 733f0ea4498a24db5b8ac048ef99983600f1eff9
+refs/heads/master: 1c0fc65e6de4e941ff483df445e721d6edb1f84b
diff --git a/trunk/drivers/net/wireless/ath/ath5k/pcu.c b/trunk/drivers/net/wireless/ath/ath5k/pcu.c
index 174412fc81f8..5212e275f1c7 100644
--- a/trunk/drivers/net/wireless/ath/ath5k/pcu.c
+++ b/trunk/drivers/net/wireless/ath/ath5k/pcu.c
@@ -496,6 +496,8 @@ void ath5k_hw_set_rx_filter(struct ath5k_hw *ah, u32 filter)
 * Beacon control *
 \****************/
 
+#define ATH5K_MAX_TSF_READ 10
+
 /**
  * ath5k_hw_get_tsf64 - Get the full 64bit TSF
  *
@@ -505,10 +507,35 @@ void ath5k_hw_set_rx_filter(struct ath5k_hw *ah, u32 filter)
  */
 u64 ath5k_hw_get_tsf64(struct ath5k_hw *ah)
 {
-	u64 tsf = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
+	u32 tsf_lower, tsf_upper1, tsf_upper2;
+	int i;
+
+	/*
+	 * While reading TSF upper and then lower part, the clock is still
+	 * counting (or jumping in case of IBSS merge) so we might get
+	 * inconsistent values. To avoid this, we read the upper part again
+	 * and check it has not been changed. We make the hypothesis that a
+	 * maximum of 3 changes can happens in a row (we use 10 as a safe
+	 * value).
+	 *
+	 * Impact on performance is pretty small, since in most cases, only
+	 * 3 register reads are needed.
+	 */
+
+	tsf_upper1 = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
+	for (i = 0; i < ATH5K_MAX_TSF_READ; i++) {
+		tsf_lower = ath5k_hw_reg_read(ah, AR5K_TSF_L32);
+		tsf_upper2 = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
+		if (tsf_upper2 == tsf_upper1)
+			break;
+		tsf_upper1 = tsf_upper2;
+	}
+
+	WARN_ON( i == ATH5K_MAX_TSF_READ );
+
 	ATH5K_TRACE(ah->ah_sc);
 
-	return ath5k_hw_reg_read(ah, AR5K_TSF_L32) | (tsf << 32);
+	return (((u64)tsf_upper1 << 32) | tsf_lower);
 }
 
 /**
diff --git a/trunk/drivers/net/wireless/ath/ath9k/hw.c b/trunk/drivers/net/wireless/ath/ath9k/hw.c
index 35f5cf40a990..894f5fc7489e 100644
--- a/trunk/drivers/net/wireless/ath/ath9k/hw.c
+++ b/trunk/drivers/net/wireless/ath/ath9k/hw.c
@@ -2420,14 +2420,25 @@ void ath9k_hw_write_associd(struct ath_hw *ah)
 }
 EXPORT_SYMBOL(ath9k_hw_write_associd);
 
+#define ATH9K_MAX_TSF_READ 10
+
 u64 ath9k_hw_gettsf64(struct ath_hw *ah)
 {
-	u64 tsf;
+	u32 tsf_lower, tsf_upper1, tsf_upper2;
+	int i;
+
+	tsf_upper1 = REG_READ(ah, AR_TSF_U32);
+	for (i = 0; i < ATH9K_MAX_TSF_READ; i++) {
+		tsf_lower = REG_READ(ah, AR_TSF_L32);
+		tsf_upper2 = REG_READ(ah, AR_TSF_U32);
+		if (tsf_upper2 == tsf_upper1)
+			break;
+		tsf_upper1 = tsf_upper2;
+	}
 
-	tsf = REG_READ(ah, AR_TSF_U32);
-	tsf = (tsf << 32) | REG_READ(ah, AR_TSF_L32);
+	WARN_ON( i == ATH9K_MAX_TSF_READ );
 
-	return tsf;
+	return (((u64)tsf_upper1 << 32) | tsf_lower);
 }
 EXPORT_SYMBOL(ath9k_hw_gettsf64);